Copy Rotation Constraint not working when paired with a Shrinkwrap
I'm always suspicious of copying rotation (or scale, or transforms) from vertices.  Why?  Because vertices don't have those characteristics.  What is a vertex group's rotation?  What is its scale?  Those aren't questions with clear answers.  Blender might try to give them those characteristics, for purposes of a constraint, but it's really weird that it does, and, for a few reasons, I'd expect poor behavior from Blender when trying to do that stuff-- not least, because it's not likely to get very intensive testing from users.
What would I do?  I would shrinkwrap two empties to the ocean, then damped track one and locked track the other:

Empties have been scaled up and changed to sphere display to improve visibility.  Shrinkwrap constraints on empties are not shown.